EFFECT OF HIGH PRESSURE ON THE ACCUMULATION OF IMP AND ON THE STABILITY OF AMP DEAMINASE IN RABBIT SKELETAL MUSCLE

This study evaluated the effect of high pressure on rabbit skeletal muscle, specifically on the production of inosinic acid (IMP), one of “umami” components, and on the activity of adenosine triphosphate (AMP) deaminase, which plays a role in the conversion of AMP to IMP. By increasing the pressure (0.1 to 300 MPa), nucleotide analysis showed that IMP content in muscle increased instantly with a concomitant decrease in ATP content. The IMP content of muscle at 300 MPa was approximately 15% higher than with lower pressures (0.1–200 MPa) when stored for 1 week at 4C after pressurization. These results suggested that the metabolism of nucleotides in muscle was not significantly impaired by pressure treatment. At 300 MPa, AMP deaminase maintained approximately 70% of the activity at 0.1 MPa. In contrast, the activity of purified AMP deaminase was completely lost at 200 MPa, and irreversible conformational changes were observed by in situ fluorescence spectroscopy. These results indicated that purified AMP deaminase was irreversibly denatured under pressure as high as 300–400 MPa.     

冷藏条件下蟹肉中ATP关联产物含量变化及其降解途径的探究

以中华绒螯蟹及三疣梭子蟹为研究对象,测定其在冷藏条件下肌肉组织中ATP关联产物种类及含量变化,并对2种蟹ATP降解途径进行探究。结果发现,在中华绒螯蟹和三疣梭子蟹肉中共检测出8种三磷酸腺苷(ATP)关联产物,分别为ATP、二磷酸腺苷(ADP)、单磷酸腺苷(AMP)、肌苷酸(IMP)、腺苷(Ad R)、次黄嘌呤核苷(Hx R)、次黄嘌呤(Hx)和黄嘌呤(Xt),且2种蟹检出种类相同;在贮藏过程中,2种蟹肉中ATP含量持续下降,2 d后分别下降了97%和93%,ADP、AMP、IMP、Hx R均先上升后下降,Hx和Xt持续上升,同时检测到少量Ad R;推测中华绒螯蟹和三疣梭子蟹死后ATP降解途径相同且有2条,一条途径为ATP→ADP→AMP→IMP→Hx R→Hx→Xt,另一条为ATP→ADP→AMP→Ad R→Hx R→Hx→Xt;根据ATP的降解途径,将K值修正为Ks值,通过线性拟合发现Ks值与中华绒螯蟹及三疣梭子蟹感官评分之间有极显著的相关性。      

不同宰前断水时间对肉鸭食用品质及能量代谢的影响

本研究以38日龄肉鸭的胸肉为研究对象,研究了不同宰前断水时间(0 h、1 h、3 h、5 h)对肉鸭食用品质及能量代谢相关限速酶活力与产物的影响,包括p Hi(初始p H值)、p Hu(最终p H值)、色泽、蒸煮损失率、加压失水率、剪切力、肌糖原、乳酸、ATP、ADP、AMP、IMP、己糖激酶、丙酮酸激酶、肌酸激酶、乳酸脱氢酶等,并对结果进行相关性分析。研究结果表明,断水处理过的肉鸭,其鸭胸肉的丙酮酸激酶活力与ATP含量呈显著负相关;己糖激酶活力与肌糖原含量有良好的正相关性;5 h断水组的IMP水平最低,ATP含量也维持在较高水准,肌糖原含量最高;经过5 h断水后的肉鸭,其鸭胸肉的p Hi显著低于3 h内断水组,使其肉质下降。综上可得,对肉鸭进行不超过5 h的短时间宰前断水处理,其食用品质、能量代谢指标处于相对较好的水平,易最大程度缓解应激,并保持肉质最佳。     

Hydrophilic interaction chromatographic determination of adenosine triphosphate and its metabolites

A new HPLC method based on hydrophilic interaction chromatography (HILIC) has been developed for the simultaneous analysis of adenosine triphosphate (ATP), adenosine diphosphate (ADP), adenosine monophosphate (AMP), inosine monophosphate (IMP), inosine (Ino), hypoxanthine (Hx) and nicotinamide adenine dinucleotide (NAD⁺) in pork loin muscle. The chromatographic analysis has been developed using a zwitterionic polymeric column and it has been optimised in terms of linearity, repeatability, reproducibility and recovery. Detection limit values of 0.10, 0.15, 0.05, 0.16, 0.16, 1.72 and 0.15 μg/mL for ATP, ADP, AMP, IMP, Ino, Hx and NAD⁺ respectively were achieved. A comparison between the pork meat concentrations of the compounds analysed by hydrophilic interaction chromatography (HILIC), using a ZIC®-pHILIC column, and ion-pair reversed-phase chromatography (IP-RP-HPLC), using a Zorbax Eclipse XDB-C18 column, has been done, concluding that the new chromatographic methodology constitutes a valid and reliable alternative to the existing methods. Finally, this method has also proved to be very effective in the isolation of guanosine, guanosine monophosphate (GMP), guanosine diphosphate (GDP), guanosine triphosphate (GTP), creatinine (Cn) and uric acid (UA) from a standards mixture.     

北京油鸡肉4 ℃贮藏过程中的品质及风味变化

北京油鸡是我国珍贵地方品种,为了解其鸡胸肉在4 ℃真空包装冷藏过程中的风味及品质变化规律,测定 其在贮藏过程中的挥发性盐基氮含量、菌落总数、感官评分、硫代巴比妥酸反应物值、总脂肪酸、肌苷酸及其他三 磷酸腺苷代谢物含量的变化,并利用电子鼻技术测定其在贮藏过程中的挥发性风味整体变化,与感官评分建立回归 方程。结果表明：综合各项理化、微生物及感官指标,真空包装北京油鸡鸡胸肉在4 ℃冷藏过程中的贮藏期为6 d; 脂肪氧化、不饱和脂肪酸和鲜味核苷酸的含量影响其贮藏过程中风味的劣变,并且利用电子鼻检测技术可以有效预 测其品质变化。     

不同贮藏条件下鸡肉肌苷酸含量的变化规律

为了探讨肌苷酸在冷藏和冷冻期间产生和降解规律,以70日龄黄羽肉鸡为实验材料,连续7 d测量4 ℃冷藏期间胸肌IMP、HxR、Hx、ADP、AMP和IMPc含量以及-20 ℃不同冷冻时间鸡肉IMP及其代谢物含量。结果显示:冷藏第2 d和第5 d IMP含量有显著降解,分别为屠宰后4 h的66%和45%。Hx含量在第2 d和第5 d极显著增加,分别为屠宰后4 h的2.6倍和4.6倍。HxR含量第4 d达到最大值,之后快速下降。IMPc含量从第5 d开始降解趋势明显。冷冻1周内IMP、Hx和HxR含量变化均不大。IMP含量冷冻1个月、210 d和540 d后分别为屠宰后4 h的65%、41%和6%,冷冻1个月到4个月之间变化不大。Hx和HxR含量分别在冷冻30 d和300 d时最高。IMPc含量冷冻210 d和540 d时下降极显著,分别为屠宰后4 h的84%和42%。因此,建议鸡肉4 ℃冷藏保存时货架期4 d为宜;-20 ℃冷冻保存时1周最宜,鸡肉冷冻保存时间最好不超过4个月。     

Concentration of Umami Compounds in Pork Meat and Cooking Juice with Different Cooking Times and Temperatures

This study examined the concentrations of umami compounds in pork loins cooked at 3 different temperatures and 3 different lengths of cooking times. The pork loins were cooked with the sous vide technique. The free amino acids (FAAs), glutamic acid and aspartic acid; the 5′‐nucleotides, inosine‐5′‐monophosphate (IMP) and adenosine‐5′‐monophosphate (AMP); and corresponding nucleoside inosine of the cooked meat and its released juice were determined by high‐performance liquid chromatography. Under the experimental conditions used, the cooking temperature played a more important role than the cooking time in the concentration of the analyzed compounds. The amino acid concentrations in the meat did not remain constant under these experimental conditions. The most notable effect observed was that of the cooking temperature and the higher amino acid concentrations in the released juice of meat cooked at 80 °C compared with 60 and 70 °C. This is most likely due to the heat induced hydrolysis of proteins and peptides releasing water soluble FAAs from the meat into the cooking juice. In this experiment, the cooking time and temperature had no influence on the IMP concentrations observed. However, the AMP concentrations increased with the increasing temperature and time. This suggests that the choice of time and temperature in sous vide cooking affects the nucleotide concentration of pork meat. The Sous vide technique proved to be a good technique to preserve the cooking juice and the results presented here show that cooking juice is rich in umami compounds, which can be used to provide a savory or brothy taste.     

POSTMORTEM CHANGES IN QUALITY INDICES OF ICE-STORED FLOUNDER (PARALICHTHYS PATAGONICUS)

The characteristics of flounder (Paralichthys patagonicus) were evaluated during a 12‐day period of storage in ice by monitoring the biochemical, microbiological and sensory parameters. The adenosine‐5′‐triphosphate and adenosine‐5′‐diphosphate were not detected, and the initial content of adenosine‐5′‐monophosphate (AMP) rapidly decreased to zero. Inosine‐5′‐monophosphate (IMP) but not adenosine (Ado) was present in muscle extracts. The AMP deaminase activity was found in the muscle. Conversely, the Ado deaminase activity was not detected. A 55% decrease in IMP concentration occurred during the first 2 days of storage. The inosine content was barely detectable (<0.1 μmol/g), probably because of the high nucleoside phosphorylase activity in the muscle. Hypoxanthine significantly (P < 0.01) increased up to the seventh day and then remained approximately constant. The muscle pH fluctuated between 6.6 and 7.0. The iced flounder was microbiologically acceptable for up to 7 days with aerobic plate counts reaching <10⁷ cfu/g. The sensory score, determined by the Quality Index Method, linearly increased (r² = 0.96) with the keeping time. All the parameters, including the K‐value, indicated that the shelf life of iced flounder was 7 days.     

Non-volatile taste active compounds in the meat of Chinese mitten crab (Eriocheir sinensis)

The non-volatile taste active compounds, including soluble sugars, succinic acid, free amino acids and flavour 5′-nucleotides in the meat of Chinese mitten crab (Eriocheir sinensis) were analyzed, and their taste impacts were evaluated by taste active values (TAVs) and equivalent umami concentration (EUC) methods. The total free amino acid content of crab meat was 20.9 mg/g. Arginine, glycine and alanine were the major free amino acids, accounting for more than 70% of the total free amino acids. 5′-Adenosine monophosphate (AMP) was the main flavour 5′-nucleotide (75.3 mg/100 g), followed by 5′-inosine monophosphate (IMP) (34.4 mg/100 g) and 5′-guanosine monophosphate (GMP) (2.3 mg/100 g). Arginine, glycine, alanine, glutamic acid, IMP and AMP were of high TAV (greater than one), and they had strong taste impacts on the crab meat flavour. Glycine and alanine contributed to the major sweet taste, while glutamic acid, IMP and AMP contributed to the strong umami taste. As the TAVs of soluble sugar, succinic acid and bitter free amino acids were lower than one, thus those compounds are likely to have insignificant impact on the taste of the crab meat. The EUC was 4.2 g MSG/100 g crab meat, which meant that the umami taste of the crab meat was very intense.     

两种饲养方式下苏尼特羊肉中鲜味物质含量及相关调控基因表达量

为研究不同饲养方式下羊肉的风味特性,以舍饲、放牧两种方式饲养的12 月龄苏尼特羊股二头肌、背最长肌、臂三头肌3 个部位为实验材料,分别测定味觉指标、鲜味物质含量以及相关调控基因表达量并进行比较分析。结果表明：放牧饲养羊肉鲜味和咸味高于舍饲饲养,苦味和涩味低于舍饲饲养;放牧饲养羊肉中的肌苷酸（inosinic acid,IMP）和肌苷（inosine,INO）含量显著高于舍饲饲养（P＜0.05）;放牧饲养羊背最长肌的腺苷一磷酸脱氨酶（adenosine monophosphate deaminase 1,AMPD1）基因表达量显著高于舍饲饲养（P＜0.05）,股二头肌的腺苷酸琥珀酸裂解酶（adenylosuccinate lyase,ADSL）和次黄嘌呤核苷酸环水解酶（aminoimidazole carboxamide ribonucleotide transformylase,ATIC）基因表达量显著高于舍饲饲养（P＜0.05）;放牧饲养羊肉AMPD1表达量与ADSL表达量之间呈极显著正相关（P＜0.01）;通过分析鲜味物质含量与调控基因表达量的相关性,发现放牧饲养羊肉IMP含量与AMPD1基因表达量之间呈极显著正相关（P＜0.01）,与ATIC基因表达量之间呈显著正相关（P＜0.05）;舍饲饲养羊肉IMP含量与ATIC基因表达量之间呈显著正相关（P＜0.05）。综上,当鲜味物质调控基因的表达量高时,肉中的鲜味物质含量也随之提高。     

热风微波联合干燥过程中南美白对虾滋味物质变化研究

为研究热风微波联合干燥过程中南美白对虾滋味物质的变化,测定了其呈味核苷酸与游离氨基酸含量,同时根据干燥过程中虾肉水分含量计算两者的干基含量变化,并计算虾肉味精当量.研究结果表明:虾肉干燥过程中,呈味核苷酸中肌苷酸含量最高,干制虾肉肌苷酸含量为405.96 mg/100 g,且始终高于阈值,对干制虾肉的鲜味形成有显著贡献;相比鲜样,干制南美白对虾中肌苷酸与单磷酸腺苷干基含量均显著下降;在虾肉中谷氨酸对鲜味形成有显著贡献,甘氨酸、丙氨酸与精氨酸对甜味形成有贡献,苯丙氨酸、赖氨酸与组氨酸能产生苦味;而在干燥过程中鲜、甜味氨基酸相对含量不断上升,分别从3.77％和17.03％上升到4.29％和35.84％;游离氨基酸总干基含量始终下降,但甘氨酸、丙氨酸、精氨酸与脯氨酸4种可以形成良好滋味的游离氨基酸干基含量上升;虾肉中肌原纤维蛋白与肌浆蛋白的干基含量均不断下降,部分分解为游离氨基酸;虾肉味精当量整体呈显著上升趋势,但在微波干燥初期(前40 s)显著下降,干制南美白对虾味精当量为3.50 g/100 g,远高于鲜虾(0.53 g/100 g),且虾肉味精当量始终远高于阈值.研究结果表明,由热风微波联合干燥引起的水分挥发与物质变化能够促进南美白对虾滋味形成.     

Early Postmortem Detection of Exudative Pork Meat Based on Nucleotide Content

The content of nucleotide metabolites in the muscle L. dorsi was analyzed for the detection of pale, soft and exudative (PSE) pork meats at just 2 h postmortem. PSE meat was characterized by significantly lower (p < 0.05) amounts of adenosine 5'-triphosphate (ATP) and higher adenosine 5'-monophosphate (AMP), inosine 5'-monophosphate (IMP), inosine (ino) and hypoxanthine (hyp) than normal meat. IMP and ino classified all the samples from both groups with statistical significance (p < 0.05). The K₀ value, R' value and IMP/ATP ratios were also useful indicators for full distinction of PSE meats. Thus, the assay of any of these nucleotide metabolites may allow a good detection of PSE meats at very short, only 2 h, postmortem time.     

三个品种白切鸡食用品质评价

为探明不同原料鸡品种对白切鸡食用品质的影响,本研究以中国南方地区经常食用的三个品种鸡（麻黄、土二、黄油）为原料,以传统方法制作的白切鸡胸肉和腿肉为研究对象,采用标准或权威方法对其食用品质相关指标进行测定及主成分分析,然后选择食用品质较好品种的鸡胸和鸡腿进行九点喜好性感官评价。结果表明,不同品种白切鸡的鸡胸肉和鸡腿肉的pH、水分、色度等理化指标均存在显著性差异（P<0.05）。麻黄品种白切鸡的pH和水分含量高,剪切力小,肉质松软多汁,味道鲜美;箱型图的离散区间小,麻黄鸡品质指标稳定。黄油品种白切鸡的pH和水分含量低,肉质柔韧,色泽亮黄;箱型图的离散区间大,剪切力、水分含量波动大。土二品种白切鸡的品质指标介于麻黄和黄油之间。主成分分析显示麻黄、土二品种不同部位的理化指标接近,与黄油品种区分明显。综合pH、水分、质构指标分析,麻黄品种白切鸡口感柔嫩,食用品质稳定。针对麻黄品种白切鸡的感官喜好性评价显示,麻黄品种白切鸡胸肉比鸡腿肉整体喜好度高,与理化指标测定结果吻合。本研究可为白切鸡加工原料的选择提供参考,也为完善白切鸡食用品质数据库及白切鸡熟食制品的标准化提供理论依据。     

Effects of pithing on pH, creatine phosphate and ATP-related compounds of beef Psoas major and Longissimus dorsi muscles

The effects of pithing at slaughter on meat quality were studied in M. longissimus dorsi (LD muscle) and M. psoas major (PM muscle) from steers. Ten steers, half of them pithed and the others not pithed at slaughter, were used for determining pH values and concentrations of creatine phosphate (CP), adenosine triphosphate (ATP) and its breakdown products in the muscles at 2·0 h post mortem. CP was not detected in any PM muscles from pithed steers and no significant differences were observed between pithed and non-pithed steers on the mean values of pH and any compounds, but significant differences were observed in the variance of pH value, ATP, (inosine monophosphate IMP) and inosine levels in PM muscles and of (adenosine diphosphate ADP) and IMP levels in LD muscles. When two steers with excitable temperament were excluded from the pithed group significant differences of variance between the treatments were observed only in PM muscles. The pithing procedure thus affects the levels of pH and of some of the ATP-related compounds in the PM but not in LD muscles.     

Establishment of a Freshness-Evaluating Standard for Chilled Yellow Chicken Meat

There is still no uniform criterion to evaluate the freshness of chilled yellow chicken meat in China. Here, we combined traditional methods, which were sensory evaluation, adenosine triphosphate (ATP) and inosine monophosphate (IMP) contents with a novel technology, electronic nose analysis, to determine the freshness of chilled yellow chicken meat. The contents of ATP and IMP in meat were detected by portable ATP detector and high-performance liquid chromatography (HPLC), respectively. In the first 3 days post-slaughter (dps), sensory evaluation scores were greater than or equal to 4, which indicate freshness. Chicken meat was deteriorated at 6 dps. As chemical indicators, IMP content was higher than ATP content, and both gradually decreased, with fluctuations. The most significant differences appeared at 3–5 days, similar to sensory evaluation results. All indicators above were different between male and female, the same rule was available between breast and thigh. We were able to distinguish the storage time, different body regions, and odors of samples using electronic nose. In the first 3 dps, few changes were found in the G ₀/G eigenvalues for each sensor, which all reached a minimum at 4 dps. In conclusion, the traditional methods and novel technology are fit for evaluating freshness, and the electronic nose is recommended to evaluate the freshness of chicken meat owing to greater speed, ease, and accuracy. To summarize the results of the three tests, we rank meat at or before 3 dps stored at 4 °C as “fresh grade,” from 3 to 5 dps as “second fresh grade,” and 6 dps and later as “non-fresh grade.”     

Concentration of Creatine Phosphate, Adenine Nucleotides and Their Derivatives in Electrically Stimulated and Nonstimulated Beef Muscle

The concentration of creatine phosphate (CP), adenosine tri-, di- and monophosphate (ATP, ADP and AMP, respectively), inosine monophosphate (IMP) and inosine in longissimus muscle removed from electrically stimulated (ES) and nonstimulated (NS) beef sides was enzymatically determined. After aging the carcass 7 days, steaks were removed for flavor evaluation. R values (absorbance ratios) were obtained from muscle samples removed over time from both sides. Data indicate more rapid catabolism of CP, ATP, and ADP in ES samples, with subsequent fluctuations in IMP and inosine concentration. At 12 and 24 hr post-stimulation, ES samples had more inosine; however, this difference did not exist after aging. Flavor differences were not observed after the 7-day aging period. R values parallel the degradation of adenine nucleotides and indicate rapid onset of rigor mortis in ES muscle.     

5'-Adenylic Acid Deaminase in Porcine Muscle

SUMMARY— The 5'-adenylic deaminase activity and AMP and IMP levels of several porcine skeletal muscles were determined on samples from 14 Poland China pigs excised immediately following exsanguination. There were no significant (P > .0.5) differences in adenylic acid deaminase activity within or between the longissimus dorsi, gluteus medius or rectus femoris muscles even though muscle morphology varied from dark, firm and dry to pale, soft and exudative. Likewise no significant (P > .05 differences in AMP or IMP levels were observed in the longissimus dorsi and gluteus medius muscles. Simple correlation coefficients between muscle pH and adenylic acid deaminase activity indicated positive relationships between enzyme activity and muscle pH at 15 and 45 min post-mortem in all muscles studied. IMP concentration was negatively related to pH of the muscle.     

蒸制鲟鱼肉特征性滋味组分的鉴定

为明确传统热加工鲟鱼肉特征性滋味组分,对蒸制鲟鱼肉中游离氨基酸、核苷酸、有机酸、甜菜碱及无机离子等滋味组分进行定量分析,并结合滋味活性值、滋味组分减缺、添加及重组实验探究蒸制鲟鱼肉的关键味觉化合物。结果表明：蒸制16 min鲟鱼肉的关键味觉化合物为甘氨酸、谷氨酸、丙氨酸、5’-一磷酸腺苷、5’-一磷酸肌苷、乳酸、琥珀酸、K＋、Na＋和Cl－;将10 种关键味觉化合物按其天然含量溶解在超纯水中制备简化重组液,简化重组液能够较为完整地复制完全重组液的味道,但与天然提取液相比,在鲜味上仍有所欠缺。     

反相高效液相色谱法测定中国对虾肉中的呈味核苷酸

核苷酸5＇-CMP、5＇-UMP、5＇-GMP、5＇-IMP、5＇-AMP 等是食品重要的鲜味物质。采用C18 高效液相色谱柱,以甲醇与0.05mol/L KH2PO4 溶液1:1(V/V)为流动相,梯度洗脱,能将其很好地分离。DAD 检测器在260nm处检测,各呈味核苷酸的测定标准曲线在0.00～0.10mg/ml 的范围内呈很好的线性关系,R2 分别在0.9902～1.0000之间。对中国对虾肉中的呈味核苷酸进行测定,结果表明：加标回收率在99.96%～100.34% 之间,变异系数在0.04%～0.4% 之间。方法的精密度和准确度均较高,可应用于食品中呈味核苷酸的分析检测。     

武昌鱼宰后4℃冷藏条件下品质变化规律

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